The present invention relates to a washing apparatus for a filter press designed so that when filter plates are moved one by one toward a movable end plate upon completion of each filtration cycle to successively separate each filter plate from an adjacent one for removal of a cake held therebetween, it sprays a washing liquid against a filter sheet spread over filter plates or against a filter surface with such filter sheet removed therefrom, thereby effecting automatic washing of the filter sheet or filter surface.
There have been two types of such apparatuses, a first type exemplified by British Pat. No. 1,271,192 wherein movement of a spray pipe toward and away from between separated filter plates and washing operation are effected by the linear to-and-from movement of the spray pipe, and a second type exemplified by German Pat. No. 1,611,097 wherein washing is effected by turning a spray pipe toward and away from between separated filter plates and linearly reciprocating the advanced spray pipe. In the first type, the movement of the spray pipe is simple but there is required a cylinder having a length corresponding to the stroke thereof and projecting a substantial distance outwardly of the filter press, thus increasing the size of the whole equipment and complicating the mechanism. Further, a device required for moving the spray pipe from one end to the other of the machine in the direction of movement of the filter plates occupies a very large space in the building in which the filter press is installed. Therefore, the installation of a filter press having a washing apparatus or the attachment of a washing apparatus to an existing filter press is difficult.
In the second type, a spray pipe disposed above the filter plates is rotated around an axis separate therefrom to and fro between a waiting position outside of the filter plates and a washing position, requiring so large a swing diameter that it projects a substantial distance beyond the filter plates even when it is in the waiting position. Further, the reciprocating movement in the washing position is effected by a cylinder, which upwardly projects a substantial distance. Therefore, the washing apparatus has the disadvantage of making too large the size of the upper portion of the space occupied by the filter press.
In either type, the necessary movement of the spray pipe is effected by a cylinder, a complicated control mechanism having a number of fluid handling elements incorporated therein is required and yet a secure and stable action can hardly be expected. Further, not only in the first type but also in the second type, during the rotation of the spray pipe, washing is impossible since no spray is given to the filter press. Therefore, washing is only effected during a simple to-and-fro movement of the spray pipe and hence the washing effect is low.